The present invention relates to a method for calibrating a detection device which is designed for the three-dimensional geometrical detection of an environment and which comprises at least one inertial measurement system for computationally determining a trajectory of the detection device. In addition, the invention also relates to a detection device designed for performing such a method.
A detection device of the generic type is described in DE 10 2009 040 468 A1, for example. Said detection device comprises a laser scanner, with the aid of which an environment can be detected three-dimensionally. The environment can be, for example, an industrial installation or a production facility. In order that the environment can be imaged correctly and precisely from the data detected by means of the laser scanner, it is obviously of great importance for the position and the orientation of the detection device to be known as accurately as possible at every point in time of measurement. Here and hereinafter, the position of the detection device is understood to mean the location of a fixed referential point of the detection device; the orientation indicates the orientation of the axes of an imaginary, intrinsic coordinate system of the detection device. The referential point of the detection device can be, for example, the coordinate origin of the imaginary, intrinsic, coordinate system of the detection device. Therefore, position and orientation have in each case three mutually independent and in total six mutually independent degrees of freedom.
In many cases, GPS signals or other global navigation signals can be used for determining position and orientation of the detection device. However, such signals cannot be received in just any environment, for example in shielded buildings. For this purpose, the known detection devices (for example that described in DE 10 2009 040 468 A1) comprise an inertial measurement system, with the aid of which it is possible to determine the accelerations in three translation directions and three rotation directions. If initial position, initial orientation, initial velocity and initial angular velocity are known, then the position and the orientation of the detection device can be determined therefrom in principle by double temporal integration at any later point in time, even without GPS or other navigation signals being available.
On account of mechanical and computational inaccuracies, however, only an approximate determination of position and orientation is possible. Over time, deviations (a so-called drift) occur between the position and orientation determined with the aid of the inertial measurement system and the actual position and orientation. Without countermeasures, the three-dimensional imaging of the environment also becomes more and more inaccurate over time as a result.